The present invention relates to an endothermal engine provided with a device for purifying the blow-by gases of the block of this engine.
As is known, the blocks of endothermal engines are provided with a bleed circuit adapted to discharge outside this block the so-called "blow-by" gases, i.e. gases that are drawn down by the cylinders into the block via the piston segments. The bleed is necessary both to prevent an increase of pressure within the block and to offset the volume variations due to the movement of the pistons.
The blow-by gases contain finely atomised oil particles as well as particles of non-combusted carbon materials (particulates) having dimensions of the order of some .mu.m, typically between 5 and 8 .mu.m.
The bleed circuit is in some cases of the open type, i.e. it discharges the blow-by gases into the atmosphere; in this case the oil and the particulates have to be separated from the gases for obvious reasons of environmental and health protection (the particulates have carcinogenic effects).
The bleed circuit is in some cases of the closed type and recirculates the blow-by gases to the engine intake in order to ensure the complete combustion of the particulates. In this case as well, however, the separation of the oil and the particulates from these gases raises a problem; the oil and the particulates tend to form resinous sediments on the components through which the gases pass before reaching the cylinders (in particular on the valves and, in the case of turbocharged engines, in the compressor and the intercooler where they greatly reduce the heat exchange), compromising the correct operation of these components. Moreover, in vehicles fitted with catalytic converters, the combustion of any engine oil recirculated to the intake has damaging effects on the catalytic converter and on the lambda probe.
While purifier devices of various types have therefore been proposed, they all have drawbacks.
For instance, impact separators are known in which the flow of gas interacts with walls which cause abrupt changes of direction of this flow; separators of this type are not, however, very efficient as regards the separation of the particulates, since the average dimensions of the particulates are too small, and are very bulky. The use of filter members of a conventional type has also proved to be unsatisfactory per se as they cause substantial losses of load and tend to clog up rapidly. Moreover, the known devices are difficult to integrate into the engine and lead to additional bulk and assembly and maintenance problems.